First off fair warning this is an article from Bleacher Report by Nate Dunlevy.
While he did point to the OL as a problem I think he let the line off a little too easy. One of his premises being that Manning took less sacks behind just as bad of line. I think the OL figured a little more into Luck's sack total than Dunlevy seems to.
The other reason I posted this isn't in the actual article ... if you read the comments Dunlevy tries to make the argument that there is no such thing as a "clutch" player ... which I completely disagree with.